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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.collection
import generic._
import TraversableView.NoBuilder
import immutable.Stream
import scala.language.implicitConversions
/** A template trait for non-strict views of iterable collections.
* $iterableViewInfo
*
* @define iterableViewInfo
* $viewInfo
* All views for iterable collections are defined by re-interpreting the `iterator` method.
*
* @author Martin Odersky
* @version 2.8
* @since 2.8
* @tparam A the element type of the view
* @tparam Coll the type of the underlying collection containing the elements.
* @tparam This the type of the view itself
*/
trait IterableViewLike[+A,
+Coll,
+This <: IterableView[A, Coll] with IterableViewLike[A, Coll, This]]
extends Iterable[A]
with IterableLike[A, This]
with TraversableView[A, Coll]
with TraversableViewLike[A, Coll, This]
with GenIterableViewLike[A, Coll, This]
{ self =>
trait Transformed[+B] extends IterableView[B, Coll] with super[TraversableViewLike].Transformed[B] with super[GenIterableViewLike].Transformed[B] {
def iterator: Iterator[B]
override def foreach[U](f: B => U): Unit = iterator foreach f
override def toString = viewToString
}
/** Explicit instantiation of the `Transformed` trait to reduce class file size in subclasses. */
private[collection] abstract class AbstractTransformed[+B] extends Iterable[B] with super[TraversableViewLike].Transformed[B] with Transformed[B]
trait EmptyView extends Transformed[Nothing] with super[TraversableViewLike].EmptyView with super[GenIterableViewLike].EmptyView
trait Forced[B] extends super[TraversableViewLike].Forced[B] with super[GenIterableViewLike].Forced[B] with Transformed[B]
trait Sliced extends super[TraversableViewLike].Sliced with super[GenIterableViewLike].Sliced with Transformed[A]
trait Mapped[B] extends super[TraversableViewLike].Mapped[B] with super[GenIterableViewLike].Mapped[B] with Transformed[B]
trait FlatMapped[B] extends super[TraversableViewLike].FlatMapped[B] with super[GenIterableViewLike].FlatMapped[B] with Transformed[B]
trait Appended[B >: A] extends super[TraversableViewLike].Appended[B] with super[GenIterableViewLike].Appended[B] with Transformed[B]
trait Filtered extends super[TraversableViewLike].Filtered with super[GenIterableViewLike].Filtered with Transformed[A]
trait TakenWhile extends super[TraversableViewLike].TakenWhile with super[GenIterableViewLike].TakenWhile with Transformed[A]
trait DroppedWhile extends super[TraversableViewLike].DroppedWhile with super[GenIterableViewLike].DroppedWhile with Transformed[A]
trait Zipped[B] extends Transformed[(A, B)] with super[GenIterableViewLike].Zipped[B]
trait ZippedAll[A1 >: A, B] extends Transformed[(A1, B)] with super[GenIterableViewLike].ZippedAll[A1, B]
private[this] implicit def asThis(xs: Transformed[A]): This = xs.asInstanceOf[This]
/** Boilerplate method, to override in each subclass
* This method could be eliminated if Scala had virtual classes
*/
protected def newZipped[B](that: GenIterable[B]): Transformed[(A, B)] = new { val other = that } with AbstractTransformed[(A, B)] with Zipped[B]
protected def newZippedAll[A1 >: A, B](that: GenIterable[B], _thisElem: A1, _thatElem: B): Transformed[(A1, B)] = new {
val other: GenIterable[B] = that
val thisElem = _thisElem
val thatElem = _thatElem
} with AbstractTransformed[(A1, B)] with ZippedAll[A1, B]
protected override def newForced[B](xs: => GenSeq[B]): Transformed[B] = new { val forced = xs } with AbstractTransformed[B] with Forced[B]
protected override def newAppended[B >: A](that: GenTraversable[B]): Transformed[B] = new { val rest = that } with AbstractTransformed[B] with Appended[B]
protected override def newMapped[B](f: A => B): Transformed[B] = new { val mapping = f } with AbstractTransformed[B] with Mapped[B]
protected override def newFlatMapped[B](f: A => GenTraversableOnce[B]): Transformed[B] = new { val mapping = f } with AbstractTransformed[B] with FlatMapped[B]
protected override def newFiltered(p: A => Boolean): Transformed[A] = new { val pred = p } with AbstractTransformed[A] with Filtered
protected override def newSliced(_endpoints: SliceInterval): Transformed[A] = new { val endpoints = _endpoints } with AbstractTransformed[A] with Sliced
protected override def newDroppedWhile(p: A => Boolean): Transformed[A] = new { val pred = p } with AbstractTransformed[A] with DroppedWhile
protected override def newTakenWhile(p: A => Boolean): Transformed[A] = new { val pred = p } with AbstractTransformed[A] with TakenWhile
// After adding take and drop overrides to IterableLike, these overrides (which do nothing
// but duplicate the implementation in TraversableViewLike) had to be added to prevent the
// overrides in IterableLike from besting the overrides in TraversableViewLike when mixed
// together in e.g. SeqViewLike. This is a suboptimal situation. Examples of failing tests
// are run/bug2876 and run/viewtest.
protected override def newTaken(n: Int): Transformed[A] = newSliced(SliceInterval(0, n))
protected override def newDropped(n: Int): Transformed[A] = newSliced(SliceInterval(n, Int.MaxValue))
override def drop(n: Int): This = newDropped(n)
override def take(n: Int): This = newTaken(n)
override def zip[A1 >: A, B, That](that: GenIterable[B])(implicit bf: CanBuildFrom[This, (A1, B), That]): That = {
newZipped(that).asInstanceOf[That]
// was: val b = bf(repr)
// if (b.isInstanceOf[NoBuilder[_]]) newZipped(that).asInstanceOf[That]
// else super.zip[A1, B, That](that)(bf)
}
override def zipWithIndex[A1 >: A, That](implicit bf: CanBuildFrom[This, (A1, Int), That]): That =
zip[A1, Int, That](Stream from 0)(bf)
override def zipAll[B, A1 >: A, That](that: GenIterable[B], thisElem: A1, thatElem: B)(implicit bf: CanBuildFrom[This, (A1, B), That]): That =
newZippedAll(that, thisElem, thatElem).asInstanceOf[That]
override def grouped(size: Int): Iterator[This] =
self.iterator grouped size map (x => newForced(x).asInstanceOf[This])
override def sliding(size: Int, step: Int): Iterator[This] =
self.iterator.sliding(size, step) map (x => newForced(x).asInstanceOf[This])
override def stringPrefix = "IterableView"
}
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